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Exoplanet Proxima B, which was recently discovered orbiting our closest neighbouring star, may have the potential to support life, new climate simulations have revealed. Ever since it was identified in August 2016, Proxima B, which stands 4.2 light years away from Earth and close to the Proxima Centauri star, has intrigued scientists. The tantalising prospect that the planet could be habitable has led many to undertake in-depth investigations. Trending: Who is David Nabarro, the UK candidate to lead the World Health Organisation? In a study now published in the journal Astronomy & Astrophysics, astrophysics and meteorology experts have worked hand in hand to explore the potential climate of Proxima B and to get a better idea of whether life could be possible on its surface. The scientists used the UK's Met office Unified Model, which has been used for years to study Earth's climate. They ran different simulations of the climate on Proxima B, if its atmosphere was similar to Earth's atmosphere. They explored a number of scenarios, changing the planet's likely orbital configuration to see if this affected the way the climate behaved on Proxima B. The scientists examined what the effects on the climate would be if the planet was in a circular orbit and tidally-locked (with the same face of the planet always facing towards its star), or if it orbited eccentrically (along an ellipse) while rotating three times on its axis for every two orbits around the star (a phenomenon known as 3:2 resonance). Most popular: Ocean pollution: Remote South Pacific island of Henderson covered in 37 million bits of plastic They find that regions of the planet would be able to host liquid water and potentially be habitable, both in the tidally-locked and eccentric 3:2 resonance configurations – although the latter is associated with more substantial areas of the planet falling within the right temperature range. "Our model is better able to take into account the variations in radiation received by the planet due to its orbit than previous models. We find that in the right conditions, Proxima B could have liquid water on its surface and could be habitable. Our model does suffer from limitations, notably we have simply assumed that the planet has an earth-like atmosphere", Nathan Mayne told IBTimes UK. "It's interesting for us to see that when we change a given parameter (over a reasonable range), the simulated climate and temperatures do not change that much. Proxima B could benefit from a remarkably stable climate regime". An important future area of research will be to investigate the composition of Proxima B's atmosphere, as this could alter the current climate projections presented by scientists. "Learning more about the composition of the exoplanet's atmosphere will be a crucial next step but we also want to learn about flare activity and how that interacts with the atmosphere. We are excited by the prospect of learning more about the climatic process happening on Proxima B - but we are not yet at the point where we can come up with a complete weather forecast", Mayne concluded. You may be interested in:


News Article | March 24, 2017
Site: www.techtimes.com

Using NASA's Hubble Telescope, Astronomers have detected a supermassive black hole being evicted from the central hub of its parent galaxy in what could be a demonstration of the immense force of gravitational waves. Scientists have suspected there are several black holes elsewhere kicked out of their galactic core and the recent discovery is considered a very strong case confirming what they assumed all the while. The black hole, which weighs more than 1 billion suns, is the first supermassive black hole found to have been evicted from its home. To propel a black hole as massive as this one from its galactic core requires an immense amount of energy. It is estimated that the energy required is equivalent to the energy of 100 supernovas exploding at the same time, study co-author Stefano Bianchi of Roma Tre University said. Stefano said their theoretical model suggested that the gravitational waves generated by the fusion of two black holes some 1 to 2 billion years ago, propelled this massive black hole spaceward. The rogue black hole was found to have moved 35,000 light-years away from the central hub of its parent galaxy 3C 186. This distance is farther than the Sun's distance from the center of the Milky Way. The researchers said this super massive black hole continues to hurtle away at a speed of 7.5 million kilometers per hour. Gravitational waves, first put forward by Albert Einstein, are ripples created when two massive objects bumped in space. These ripples are similar to the waves created when a stone is dropped into a pond. Its existence was only proven last year when the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected them having their origin from the merging of two massive black holes. "When I first saw this, I thought we were seeing something very peculiar," team leader Marco Chiaberge of the Space Telescope Science Institute said of the observed black hole. Since black holes are located at the core of their galaxies, Chiaberge said he was surprised to see a quasar off from the galaxy's central hub. Quasars are the visible and energetic signature of black holes. He said the combined data from different observation sites revealed the same stellar event. Chiaberge's paper on the phenomenon will be published in Astronomy & Astrophysics on March 30. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


News Article | April 19, 2017
Site: www.eurekalert.org

An international group of researchers led by Brazilians has identified and characterized 82 binaries in a satellite galaxy of the Milky Way In addition to solo stars like our Sun, the universe contains binary systems comprising two massive stars that interact with each other. In many binaries the two stars are close enough to exchange matter and may even merge, producing a single high-mass star that spins at great speed. Until now the number of known high-mass binaries has been very small, basically confined to those identified in our galaxy, the Milky Way. An international group of astronomers led by researchers at the University of São Paulo's Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP) in Brazil, have just extended the list of by identifying and characterizing 82 new high-mass binaries located in the Tarantula Nebula, also known as 30 Doradus, in the Large Magellanic Cloud. The LMC is a satellite galaxy of the Milky Way and is about 160,000 light years from Earth. The results of the study are described in article published in the journal Astronomy & Astrophysics. "By identifying and characterizing these 82 high-mass binaries, we have more than doubled the number of these objects, and in a completely new region with very different conditions from those found in the Milky Way," said Leonardo Andrade de Almeida, a postdoctoral fellow at IAG-USP and first author of the study. In research supervised by Augusto Damineli Neto, a full professor at IAG and a co-author of the article, Almeida analyzed the data obtained during the VLT-FLAMES Tarantula Survey and Tarantula Massive Binary Monitoring observation campaigns performed by the European Southern Observatory (ESO) from 2011. Using FLAMES/GIRAFFE, a spectrograph coupled to ESO's Very Large Telescope (VLT), which has four 8 m primary mirrors and operates in Chile's Atacama Desert, the observation campaigns collected spectral data for over 800 high-mass objects in the region of the Tarantula Nebula, so named because its glowing filaments resemble spider legs. From this total of 800 observed objects, the astronomers who worked on the two surveys identified 100 candidate binaries of spectral type O (very hot and massive) in a sample of 360 stars based on parameters such as the amplitude of variations in their radial velocity (the velocity of motion away from or toward an observer). For the last two years, Almeida has collaborated with colleagues in other countries on an analysis of these 100 candidate high-mass binaries using the FLAMES/GIRAFFE spectrograph and has managed to characterize 82 of them completely. "This represents the largest survey and spectroscopic characterization of massive binary systems every performed," he said. "It was only possible thanks to the technological capabilities of the FLAMES/GIRAFFE spectrograph." The scientific instrument developed by ESO can be used to obtain spectra for a number of objects simultaneously, and weaker objects can be observed because it is coupled to the VLT, which has large mirrors and captures more light, Almeida explained. "We can collect 136 spectra in a single observation using FLAMES/GIRAFFE," he said. "Nothing similar could be done before. Our instruments could only observe individual objects and it took much longer to characterize them." Spectroscopic analysis of the 82 binaries showed that properties such as mass ratio, orbital period (the time taken to complete one orbit) and orbital eccentricity (the amount by which the orbit deviates from a perfect circle) were highly similar to those observed in the Milky Way. This was unexpected since the LMC embodies a phase of the universe prior to the Milky Way when the largest number of high-mass stars were formed. For this reason, its metallicity - the proportion of its matter made up of chemical elements different from hydrogen and helium, the primordial atoms that gave rise to the first stars - is only half that of the binaries found in the Milky Way, whose metallicity is very close to the Sun's. "At the beginning of the universe, stars were metal-poor but chemical evolution increased their metallicity," Almeida said. This analysis of binaries in the LMC, he added, provides the first direct constraints on the properties of massive binaries in galaxies whose stars were formed in the early universe and have the LMC's metallicity. "The discoveries made during the study may provide better measurements for use in more realistic simulations of how high-mass stars evolved in the different phases of the universe. If so, we'll be able to obtain more precise estimates of the rate at which black holes, neutron stars and supernovae were formed in each phase, for example," he said. High-mass stars are the most important drivers of the chemical evolution of the universe. Because they are more massive, they produce more heavy metals, evolve more rapidly, and end their lives as supernovae, ejecting all their matter into the interstellar medium. This matter is recycled to form a new population of stars. However, Almeida went on, estimates of the chemical evolution of the universe and astrophysical predictions of the number of black holes usually take into account sole stars like our Sun, which evolve more simply. According him, when you include binaries in computing these projections, the result changes dramatically. So when making astrophysical predictions you need to consider these massive objects.


Until now, the number of known high-mass binaries has been very small, basically confined to those identified in our galaxy, the Milky Way. An international group of astronomers led by researchers at the University of São Paulo's Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP) in Brazil, has just extended the list of by identifying and characterizing 82 new high-mass binaries located in the Tarantula Nebula, also known as 30 Doradus, in the Large Magellanic Cloud. The LMC is a satellite galaxy of the Milky Way and is about 160,000 light years from Earth. The results of the study are described in article published in the journal Astronomy & Astrophysics. "By identifying and characterizing these 82 high-mass binaries, we have more than doubled the number of these objects, and in a completely new region with very different conditions from those found in the Milky Way," said Leonardo Andrade de Almeida, a postdoctoral fellow at IAG-USP and first author of the study. In research supervised by Augusto Damineli Neto, a full professor at IAG and a co-author of the article, Almeida analyzed the data obtained during the VLT-FLAMES Tarantula Survey and Tarantula Massive Binary Monitoring observation campaigns performed by the European Southern Observatory (ESO) from 2011. Using FLAMES/GIRAFFE, a spectrograph coupled to ESO's Very Large Telescope (VLT), which has four 8m primary mirrors and operates in Chile's Atacama Desert, the observation campaigns collected spectral data for over 800 high-mass objects in the region of the Tarantula Nebula, so named because its glowing filaments resemble spider legs. From this total of 800 observed objects, the astronomers who worked on the two surveys identified 100 candidate binaries of spectral type O (very hot and massive) in a sample of 360 stars based on parameters such as the amplitude of variations in their radial velocity (the velocity of motion away from or toward an observer). For the last two years, Almeida has collaborated with colleagues in other countries on an analysis of these 100 candidate high-mass binaries using the FLAMES/GIRAFFE spectrograph and has managed to characterize 82 of them completely. "This represents the largest survey and spectroscopic characterization of massive binary systems every performed," he said. "It was only possible thanks to the technological capabilities of the FLAMES/GIRAFFE spectrograph." The scientific instrument developed by ESO can obtain spectra for a number of objects simultaneously, and weaker objects can be observed because the spectrograph is coupled to the VLT, which has large mirrors and captures more light, Almeida explained. "We can collect 136 spectra in a single observation using FLAMES/GIRAFFE," he said. "Nothing similar could be done before. Our instruments could only observe individual objects and it took much longer to characterize them." Spectroscopic analysis of the 82 binaries showed that properties such as mass ratio, orbital period (the time taken to complete one orbit) and orbital eccentricity (the amount by which the orbit deviates from a perfect circle) were highly similar to those observed in the Milky Way. This was unexpected since the LMC embodies a phase of the universe prior to the Milky Way, when the largest number of high-mass stars were formed. For this reason, its metallicity—the proportion of its matter made up of chemical elements other than primordial hydrogen and helium—is only half that of the binaries found in the Milky Way, whose metallicity is very close to the sun's. "At the beginning of the universe, stars were metal-poor but chemical evolution increased their metallicity," Almeida said. This analysis of binaries in the LMC, he added, provides the first direct constraints on the properties of massive binaries in galaxies whose stars were formed in the early universe and have the LMC's metallicity. "The discoveries made during the study may provide better measurements for use in more realistic simulations of how high-mass stars evolved in the different phases of the universe. If so, we'll be able to obtain more precise estimates of the rate at which black holes, neutron stars and supernovae were formed in each phase, for example," he said. High-mass stars are the most important drivers of the chemical evolution of the universe. Because they are more massive, they produce more heavy metals, evolve more rapidly, and end their lives as supernovae, ejecting all their matter into the interstellar medium. This matter is recycled to form a new population of stars. However, Almeida went on, estimates of the chemical evolution of the universe and astrophysical predictions of the number of black holes usually take into account sole stars like our sun, which evolve more simply. According him, when you include binaries in computing these projections, the result changes dramatically. So when making astrophysical predictions, it is important to consider these massive objects. Explore further: No close partner for young, massive stars in Omega Nebula More information: L. A. Almeida et al, The Tarantula Massive Binary Monitoring, Astronomy & Astrophysics (2017). DOI: 10.1051/0004-6361/201629844


News Article | May 24, 2017
Site: phys.org

A near- and mid-infrared image of galaxy IC 342 from the Spitzer Space Telescope. The region studied by SOFIA/GREAT is the centermost zone, shown inside the yellow box, appearing white and purple in this false-color representation. Credit: SOFIA An international team of researchers used NASA's Stratospheric Observatory for Infrared Astronomy, SOFIA, to make maps of the ring of molecular clouds that encircles the nucleus of galaxy IC 342. The maps determined the proportion of hot gas surrounding young stars as well as cooler gas available for future star formation. The SOFIA maps indicate that most of the gas in the central zone of IC 342, like the gas in a similar region of our Milky Way Galaxy, is heated by already-formed stars, and relatively little is in dormant clouds of raw material. At a distance of about 13 million light years, galaxy IC 342 is considered relatively nearby. It is about the same size and type as our Milky Way Galaxy, and oriented face-on so we can see its entire disk in an undistorted perspective. Like our galaxy, IC 342 has a ring of dense molecular gas clouds surrounding its nucleus in which star formation is occurring. However, IC 342 is located behind dense interstellar dust clouds in the plane of the Milky Way, making it difficult to study by optical telescopes. The team of researchers from Germany and the Netherlands, led by Markus Röllig of the University of Cologne, Germany, used the German Receiver for Astronomy at Terahertz frequencies, GREAT, onboard SOFIA to scan the center of IC 342 at far-infrared wavelengths to penetrate the intervening dust clouds. Röllig's group mapped the strengths of two far-infrared spectral lines – one line, at a wavelength of 158 microns, is emitted by ionized carbon, and the other, at 205 microns, is emitted by ionized nitrogen. The 158-micron line is produced both by cold interstellar gas that is the raw material for new stars, and also by hot gas illuminated by stars that have already finished forming. The 205-micron spectral line is only emitted by the hot gas around already-formed young stars. Comparison of the strengths of the two spectral lines allows researchers to determine of the amount of warm gas versus cool gas in the clouds. Röllig's team found that most of the ionized gas in IC 342's central molecular zone (CMZ) is in clouds heated by fully formed stars rather than in cooler gas found farther out in the zone, like the situation in the Milky Way's CMZ. The team's research was published in Astronomy and Astrophysics, volume 591. "SOFIA and its powerful GREAT instrument allowed us to map star formation in the center of IC 342 in unprecedented detail," said Markus Röllig of the University of Cologne, Germany, "These measurements are not possible from ground-based telescopes or existing space telescopes." Researchers previously used SOFIA's GREAT spectrometer for a corresponding study of the Milky Way's CMZ. That research, published in 2015 by principal investigator W.D. Langer, et. al, appeared in the journal Astronomy & Astrophysics 576, A1; an overview of that study can be found here. Explore further: VISTA peeks through the Small Magellanic Cloud's dusty veil More information: * "[CII] 158 Micron and [NII] 205 Micron Emission from IC 342: Disentangling the Emission from Ionized and Photo-Dissociated Regions," M. Röllig et al., 2016 July, Astronomy & Astrophysics doi.org/10.1051/0004-6361/201526267 * "Ionized Gas at the Edge of the Central Molecular Zone," W. D. Langer et al., 2015 April, Astronomy & Astrophysics doi.org/10.1051/0004-6361/201425360


News Article | May 26, 2017
Site: motherboard.vice.com

Sexism in astronomy has become a topical issue in recent years, especially after prominent UC Berkeley professor Geoffrey Marcy was forced to resign in 2015 over sexual harassment charges from many of his female students, which led to an outpouring of related stories. Discrimination against female astronomers has been shown to impact everything from equal pay to access to leadership roles. Now, a quantitative study published on Friday in Nature Astronomy demonstrates that gender bias in astronomical research extends even to journal citations, which are an indicator of academic prestige and are linked with better access to grant money, speaking engagements, and professional advancement. Led by Neven Caplar, a PhD student at ETH Zürich's Institute of Astronomy, the new research found that papers with male lead authors were cited 10 percent more frequently than papers led by women, even after controlling for non-gender-specific disparities such as seniority, team size, publication date, field, and academic institution. This exposes "clear indications of the existence of gender bias in astronomy," said Caplar and his colleagues. The team reached this conclusion after using machine-learning to analyze a dataset of over 200,000 papers published between 1950 and 2015 in five influential journals: Astronomy & Astrophysics, The Astrophysical Journal, Monthly Notices of the Royal Astronomical Society, Nature, and Science. The team identified the genders of first authors by running bibliographic information through databases such as SexMachine or Gender API. They scrubbed any research in which the lead author's gender was inconclusive, reducing the final sample to 149,741 papers. In cases where first authors used their initials—a tactic women researchers disproportionately use to avoid gender bias—Caplar's team took extra measures to identify exceptions in publishing records that exposed authors' full names. Read More: Bill Nye Didn't 'Censor' Gender Science, He Updated it Because That's How Science Works "Even if you [normally] use your initials, but you used your full name once in your career, we could find you and match you by your surname and the first letter of your initials," Caplar told me over Skype. Women who changed their maiden names could also be identified this way. However, Caplar added that initialled female authors with only a few papers under their belts would be trickier to track down. After the papers had been split by gender, the team cross-examined the various properties of male-led research, such as research field, paper length, and professional experience. They matched these non-gender-specific qualities with the female-led research and predicted the citation rate for female first authors if there were no gender bias, and compared it to the actual results shown in the sample. As visualized above, women have been closing the citation gap steadily over the past half-century, but they still remain underrepresented within this metric. The study also reveals a range of gender disparities across astronomical specialities. "We divided the subfields into six categories, and you can clearly see that men are more prominent in instruments and methods papers," Caplar told me. "On the other hand, you can see a strong increase in the number of women writers in the planetary science papers, because planets are a hot topic, and there are more women in astronomy now than before." The fact that female astronomers are systematically cited less often than men likely has negative ricochet effects for their careers. When combined with previous studies reporting wage gaps of 25 to 40 percent between male and female astronomers, a tendency for female astronomers to have fewer children than they'd like, and the underrepresentation of women in publicly valued roles, such as astronauts or Nobel Prize recipients, it's clear there's much work still to be done to even the astronomical playing field. This bias is not only a burden for women trying to get ahead in astronomy or another scientific field. As Caplar and his co-authors point out, "a pool of researchers from a wide range of backgrounds, experiences and perspectives maximizes creativity and innovation" in science. When equally qualified women are unequally represented, the astronomy community as a whole suffers, as does our understanding and exploration of worlds beyond our own. Subscribe to Science Solved It, Motherboard's new show about the greatest mysteries that were solved by science.


News Article | May 12, 2017
Site: spaceref.com

For the first time, astronomers have detected a magnetic field associated with the Magellanic Bridge, the filament of gas stretching 75 thousand light-years between the Milky Way Galaxy's nearest galactic neighbours: the Large and Small Magellanic Clouds (LMC and SMC, respectively). Visible in the southern night sky, the LMC and SMC are dwarf galaxies that orbit our home galaxy and lie at a distance of 160 and 200 thousand light-years from Earth respectively, "There were hints that this magnetic field might exist, but no one had observed it until now," says Jane Kaczmarek, a PhD student in the School of Physics, University of Sydney, and lead author of the paper describing the finding. Such cosmic magnetic fields can only be detected indirectly, and this detection was made by observing the radio signals from hundreds of very distant galaxies that lie beyond the LMC and SMC. The observations were made with the Australia Telescope Compact Array radio telescope at the Paul Wild Observatory in New South Wales, Australia. "The radio emission from the distant galaxies served as background 'flashlights' that shine through the Bridge," says Kaczmarek. "Its magnetic field then changes the polarization of the radio signal. How the polarized light is changed tells us about the intervening magnetic field." A radio signal, like a light wave, oscillates or vibrates in a single direction or plane; for example, waves on the surface of a pond move up and down. When a radio signal passes through a magnetic field, the plane is rotated. This phenomenon is known as Faraday Rotation and it allows astronomers to measure the strength and the polarity--or direction--of the field. The observation of the magnetic field, which is one millionth the strength of the Earth's, may provide insight into whether it was generated from within the Bridge after the structure formed, or was "ripped" from the dwarf galaxies when they interacted and formed the structure. "In general, we don't know how such vast magnetic fields are generated, nor how these large-scale magnetic fields affect galaxy formation and evolution," says Kaczmarek. "The LMC and SMC are our nearest neighbours, so understanding how they evolve may help us understand how our Milky Way Galaxy will evolve." "Understanding the role that magnetic fields play in the evolution of galaxies and their environment is a fundamental question in astronomy that remains to be answered." The paper is one of a growing number of new results that are building a map of the Universe's magnetism. According to Prof. Bryan Gaensler, Director of the Dunlap Institute for Astronomy & Astrophysics, University of Toronto, and a co-author on the paper, "Not only are entire galaxies magnetic, but the faint delicate threads joining galaxies are magnetic, too. Everywhere we look in the sky, we find magnetism." The paper appeared in the Monthly Notices of the Royal Astronomical Society. Reference: "Detection of a Coherent Magnetic Field in the Magellanic Bridge Through Faraday Rotation," 2017 May, Monthly Notices of the Royal Astronomical Society [http://dx.doi.org/10.1093/mnras/stx206, preprint: https://arxiv.org/abs/1701.05962]. Please follow SpaceRef on Twitter and Like us on Facebook.


News Article | May 12, 2017
Site: phys.org

Visible in the southern night sky, the LMC and SMC are dwarf galaxies that orbit our home galaxy and lie at a distance of 160 and 200 thousand light-years from Earth respectively, "There were hints that this magnetic field might exist, but no one had observed it until now," says Jane Kaczmarek, a PhD student in the School of Physics, University of Sydney, and lead author of the paper describing the finding. Such cosmic magnetic fields can only be detected indirectly, and this detection was made by observing the radio signals from hundreds of very distant galaxies that lie beyond the LMC and SMC. The observations were made with the Australia Telescope Compact Array radio telescope at the Paul Wild Observatory in New South Wales, Australia. "The radio emission from the distant galaxies served as background 'flashlights' that shine through the Bridge," says Kaczmarek. "Its magnetic field then changes the polarization of the radio signal. How the polarized light is changed tells us about the intervening magnetic field." A radio signal, like a light wave, oscillates or vibrates in a single direction or plane; for example, waves on the surface of a pond move up and down. When a radio signal passes through a magnetic field, the plane is rotated. This phenomenon is known as Faraday Rotation and it allows astronomers to measure the strength and the polarity—or direction—of the field. The observation of the magnetic field, which is one millionth the strength of the Earth's, may provide insight into whether it was generated from within the Bridge after the structure formed, or was "ripped" from the dwarf galaxies when they interacted and formed the structure. "In general, we don't know how such vast magnetic fields are generated, nor how these large-scale magnetic fields affect galaxy formation and evolution," says Kaczmarek. "The LMC and SMC are our nearest neighbours, so understanding how they evolve may help us understand how our Milky Way Galaxy will evolve." "Understanding the role that magnetic fields play in the evolution of galaxies and their environment is a fundamental question in astronomy that remains to be answered." The paper is one of a growing number of new results that are building a map of the Universe's magnetism. According to Prof. Bryan Gaensler, Director of the Dunlap Institute for Astronomy & Astrophysics, University of Toronto, and a co-author on the paper, "Not only are entire galaxies magnetic, but the faint delicate threads joining galaxies are magnetic, too. Everywhere we look in the sky, we find magnetism." The paper appeared in the Monthly Notices of the Royal Astronomical Society. Explore further: Giant magnetic fields in the universe More information: J. F. Kaczmarek et al. Detection of a Coherent Magnetic Field in the Magellanic Bridge through Faraday Rotation, Monthly Notices of the Royal Astronomical Society (2017). DOI: 10.1093/mnras/stx206 , On Arxiv: https://arxiv.org/abs/1701.05962


In turn, they have used that result to calculate that the Sun is approximately 7.9 kiloparsecs from the Galaxy's centre—or almost twenty-six thousand light-years. Using data from the Gaia space telescope and the RAdial Velocity Experiment (RAVE) survey, Jason Hunt and his colleagues determined the velocities of over 200,000 stars relative to the Sun. Hunt is a Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics, University of Toronto. The collaborators found an unsurprising distribution of relative velocities: there were stars moving slower, faster and at the same rate as the Sun. But they also found a shortage of stars with a Galactic orbital velocity of approximately 240 kilometres per second slower than the Sun's. The astronomers concluded that the missing stars had been stars with zero angular momentum; i.e. they had not been circling the Galaxy like the Sun and the other stars in the Milky Way Galaxy; "Stars with very close to zero angular momentum would have plunged towards the Galactic centre where they would be strongly affected by the extreme gravitational forces present there," says Hunt. "This would scatter them into chaotic orbits taking them far above the Galactic plane and away from the Solar neighbourhood." "By measuring the velocity with which nearby stars rotate around our Galaxy with respect to the Sun," says Hunt, "we can observe a lack of stars with a specific negative relative velocity. And because we know this dip corresponds to 0 km/sec, it tells us, in turn, how fast we are moving." Hunt and his colleagues then combined this finding with the proper motion of the supermassive blackhole known as Sagittarius A* ("A-star") that lies at the centre of the Galaxy to calculate the 7.9 kiloparsec distance. Proper motion is the motion of an object across the sky relative to distant background objects. They calculated the distance in the same way a cartographer triangulates the distance to a terrestrial landmark by observing it from two different positions a known distance apart. The result was published in Astrophysical Journal Letters in December 2017. The method was first used by Hunt's co-author, current chair of the Department of Astronomy & Astrophysics at the University of Toronto, Prof. Ray Calberg, and Carlberg's collaborator, Prof. Kimmo Innanen. But the result Carlberg and Innanen arrived at was based on less than 400 stars. Gaia is creating a dynamic, three-dimensional map of the Milky Way Galaxy by measuring the distances, positions and proper motion of stars. Hunt and his colleagues based their work on the initial data release from Gaia which included hundreds of thousands of stars. By the end of its 5 year mission, the space mission will have mapped well over 1 billion stars. The velocity and distance results are not significantly more accurate than other measurements. But according to Hunt, "Gaia's final release in late 2017 should enable us to increase the precision of our measurement of the Sun's velocity to within approximately one km/sec, which in turn will significantly increase the accuracy of our measurement of our distance from the Galactic centre." Explore further: Astronomers detect a fast rotating group of stars in our galaxy More information: Jason A. S. Hunt et al. DETECTION OF A DEARTH OF STARS WITH ZERO ANGULAR MOMENTUM IN THE SOLAR NEIGHBORHOOD, The Astrophysical Journal (2016). DOI: 10.3847/2041-8205/832/2/L25


News Article | February 15, 2017
Site: phys.org

The open cluster M17 (the Omega Nebula), about 5000 light years away, is one of the brightest star-forming regions in the Milky Way. This infrared image from the 2MASS catalog reveals the ten surveyed young, massive stars that lie hidden in the gas and dust in this stellar nursery. Credit: Maria Ramirez-Tannus/UvA Astronomers from Leuven (Belgium) and Amsterdam (Netherlands) have discovered that massive stars in the star-forming region M17 (the Omega Nebula) are—against expectations—not part of a close binary. They have started their lives alone or with a distant partner star. The researchers base their findings on data from the X-shooter spectrograph on ESO's Very Large Telescope in northern Chile. The study will be published in Astronomy & Astrophysics Letters. The Omega Nebula is an open cluster in the constellation Sagittarius. The cluster is at a distance of about 5,000 light years and contains some dozens of young, hot stars. Hugues Sana (University of Leuven), Maria Ramirez-Tannus, Lex Kaper and Alex de Koter (University of Amsterdam) discovered that these massive stars have surprisingly little differences in their radial velocity, the speed towards us or away from us. If these stars were binaries their radial velocity would likely differ by tens to hundreds of kilometers per second because they are in their orbits around each other. In M17 it ranges with only five kilometers per second. Most stars are not alone. Recent research shows that 70 percent of the massive stars (some 10 to 100 times the mass of the Sun), which end their lives as neutron star or black hole, has one or more near companions. As a contrast, a statistical analysis shows that only about 10 percent of the massive stars in M17 are narrow binaries. Alternatively, M17 may contain a lot of wide binaries, compared with older star forming regions harboring both narrow and wide binaries. This is the first time that such a young star-forming region is examined for the presence of binary stars. The reason is that such areas are hidden from view by the gas and dust from which the new stars are formed. It is therefore a challenge to get spectra of high quality, from which the radial velocity can be determined. First author Sana: "If M17 has indeed no narrow binaries, these systems have to appear later in evolution. Maybe they are only wide binaries, which later migrate towards each other. Co-author Ramirez-Tannus is enthusiastic about the results: "We have now observed ten of them and will study many more to understand how wide binaries change in narrow binary stars." The answer to the question whether massive stars usually live together in binaries is important for understanding of the star formation process. However, it is also an indication for the formation of the number of neutron binaries and double black holes, which eventually can produce a gravitational wave. Explore further: Simple view of gravity does not fully explain distribution of stars in crowded clusters More information: A dearth of short-period massive binaries in the young massive star forming region M17: Evidence for a large orbital separation at birth? arxiv.org/abs/1702.02153

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